1. Field of the Invention
The present invention relates generally to methods and apparatus for video or other photographic security systems.
2. Description of Related Art
Security systems using video cameras have been in use for many years.
U.S. Pat. No. 5,099,322 shows a system for detecting scene changes using a video security system. U.S. Pat. No. 5,471,239 show the system for using video frame compression and numerical comparison to detect scene changes.
In a method for monitoring a field of view for visible changes, according to the present invention, a first image is taken in a predetermined manner of the field of view to be monitored, and then an array divides the first image into a plurality of cells. The first image divided by the array is then stored, and a second image is taken in the predetermined manner of the field of view to be monitored. The array is also applied to the second image, dividing the second image into the plurality of cells. Cells are combined into predetermined groups. The groups could be individual cells, which is to say groups of one cell each. The groups could be rows of cells or columns of cells or rectangular groupings which in effect create larger cells. The predetermined groups of cells of the second image are then compared to the same groups of cells of the first image, and the number of the groups of cells that changed from the first image to the second image is computed. In some situations only certain groups of cells are compared. If a parrot is moving around in a cage, then the cells or the groups of cells which might show the parrot are not compared, or if there are several ceiling fans which are moving, then the cells or the groups of cells which show the ceiling fans might not be compared. There are also other ways of handling these problems which are also described.
In one preferred form of the method, each cell of the first image is given a numerical value based upon the information in each cell, and each cell of the second image is also given a numerical value based upon the information in each cell. Each group of cells is also given a numerical value based on the numerical value of the cells within the group. The simplest method is to make the numerical value of each group equal to the sum of the numerical values of the cells within the group, but manipulation would work as long as the numerical value of the group changes when the numerical value of its cells change. Computing how many groups of the cells changed from the first image to the second image is simply a matter of computing the difference between the numerical value of each group of cells in the second image and in the first image.
In one arrangement, each cell is a single picture element, known as a pixel. A pixel has a its own brightness ranging from 0 for black to a maximum value, typically 255, for white, and the numerical value of each cell is the brightness of the pixel. There is still a brightness number for color images, but color scales could also be used. The numerical value of each group of cells is determined by an image algorithm, which in one preferred form is simply taking the sum of the brightness for the pixels in the group. In one such arrangement, the predetermined groups of cells comprises a single group.
In one method according to the present invention, the number of the groups of cells which changed in numerical value by more than a predetermined amount is also computed.
One method, according to the present invention, also includes the step of comparing the number of the groups of cells that changed from the first image to the second image to a predetermined number. If the parrot moving in its cage, or a cat climbing on the furniture is small enough to never be in more than the predetermined number groups of cells, then if more than the predetermined number groups of cells changed, then it was not caused by the parrot or the cat.
Another method, according to the present invention, for monitoring a field of view for visible changes, includes the steps of taking a sequence of video images in a predetermined manner of the field of view to be monitored, creating a sequence of images, and creating an array which divides each of the images into a plurality of cells. Each image divided by the array is stored and the groups of cells of each image are compared to the same groups of cells of the other images. Again, this could just be predetermined groups of cells which are less than all of the groups of cells. It is then computed if there is a cyclical change in any of the predetermined groups of cells during the sequence. This cyclical change could be the rotation of a ceiling fan or the movement of a flower arrangement caused by the blowing of an air conditioner. Similar to that already described, each cell of each image is given a numerical value based upon the information in that cell, and each group of cells is given a numerical value based upon the numerical value of the cells within that group, and computing if there is a cyclical change in any of the predetermined groups of cells during the sequence becomes computing if there is a cyclical change in any of the numerical values of the predetermined groups of cells during the sequence. In a preferred form, the number of the predetermined groups of cells that changed from one image of the sequence to the next image of the sequence and was not part of a cyclical change is computed.
These and other objects, advantages and features of this invention will be apparent from the following description taken with reference to the accompanying drawing, wherein is shown a preferred embodiment of the invention.